diff mbox series

[V34,11/29] PCI: Lock down BAR access when the kernel is locked down

Message ID 20190622000358.19895-12-matthewgarrett@google.com (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show
Series None | expand

Commit Message

Matthew Garrett June 22, 2019, 12:03 a.m. UTC
From: Matthew Garrett <mjg59@srcf.ucam.org>

Any hardware that can potentially generate DMA has to be locked down in
order to avoid it being possible for an attacker to modify kernel code,
allowing them to circumvent disabled module loading or module signing.
Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
cc: linux-pci@vger.kernel.org
---
 drivers/pci/pci-sysfs.c      | 16 ++++++++++++++++
 drivers/pci/proc.c           | 14 ++++++++++++--
 drivers/pci/syscall.c        |  4 +++-
 include/linux/security.h     |  1 +
 security/lockdown/lockdown.c |  1 +
 5 files changed, 33 insertions(+), 3 deletions(-)

Comments

Kees Cook June 22, 2019, 11:55 p.m. UTC | #1
On Fri, Jun 21, 2019 at 05:03:40PM -0700, Matthew Garrett wrote:
> From: Matthew Garrett <mjg59@srcf.ucam.org>
> 
> Any hardware that can potentially generate DMA has to be locked down in
> order to avoid it being possible for an attacker to modify kernel code,
> allowing them to circumvent disabled module loading or module signing.
> Default to paranoid - in future we can potentially relax this for
> sufficiently IOMMU-isolated devices.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> Signed-off-by: Matthew Garrett <mjg59@google.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> cc: linux-pci@vger.kernel.org
> ---
>  drivers/pci/pci-sysfs.c      | 16 ++++++++++++++++
>  drivers/pci/proc.c           | 14 ++++++++++++--
>  drivers/pci/syscall.c        |  4 +++-
>  include/linux/security.h     |  1 +
>  security/lockdown/lockdown.c |  1 +
>  5 files changed, 33 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 25794c27c7a4..e1011efb5a31 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -903,6 +903,11 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
>  	unsigned int size = count;
>  	loff_t init_off = off;
>  	u8 *data = (u8 *) buf;
> +	int ret;
> +
> +	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
> +	if (ret)
> +		return ret;
>  
>  	if (off > dev->cfg_size)
>  		return 0;
> @@ -1165,6 +1170,11 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
>  	int bar = (unsigned long)attr->private;
>  	enum pci_mmap_state mmap_type;
>  	struct resource *res = &pdev->resource[bar];
> +	int ret;
> +
> +	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
> +	if (ret)
> +		return ret;
>  
>  	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
>  		return -EINVAL;
> @@ -1241,6 +1251,12 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
>  				     struct bin_attribute *attr, char *buf,
>  				     loff_t off, size_t count)
>  {
> +	int ret;
> +
> +	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
> +	if (ret)
> +		return ret;
> +
>  	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
>  }
>  
> diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
> index 6fa1627ce08d..a72258d70407 100644
> --- a/drivers/pci/proc.c
> +++ b/drivers/pci/proc.c
> @@ -13,6 +13,7 @@
>  #include <linux/seq_file.h>
>  #include <linux/capability.h>
>  #include <linux/uaccess.h>
> +#include <linux/security.h>
>  #include <asm/byteorder.h>
>  #include "pci.h"
>  
> @@ -115,7 +116,11 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
>  	struct pci_dev *dev = PDE_DATA(ino);
>  	int pos = *ppos;
>  	int size = dev->cfg_size;
> -	int cnt;
> +	int cnt, ret;
> +
> +	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
> +	if (ret)
> +		return ret;
>  
>  	if (pos >= size)
>  		return 0;
> @@ -196,6 +201,10 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
>  #endif /* HAVE_PCI_MMAP */
>  	int ret = 0;
>  
> +	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
> +	if (ret)
> +		return ret;
> +
>  	switch (cmd) {
>  	case PCIIOC_CONTROLLER:
>  		ret = pci_domain_nr(dev->bus);
> @@ -237,7 +246,8 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
>  	struct pci_filp_private *fpriv = file->private_data;
>  	int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
>  
> -	if (!capable(CAP_SYS_RAWIO))
> +	if (!capable(CAP_SYS_RAWIO) ||
> +	    security_locked_down(LOCKDOWN_PCI_ACCESS))
>  		return -EPERM;
>  
>  	if (fpriv->mmap_state == pci_mmap_io) {
> diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
> index d96626c614f5..31e39558d49d 100644
> --- a/drivers/pci/syscall.c
> +++ b/drivers/pci/syscall.c
> @@ -7,6 +7,7 @@
>  
>  #include <linux/errno.h>
>  #include <linux/pci.h>
> +#include <linux/security.h>
>  #include <linux/syscalls.h>
>  #include <linux/uaccess.h>
>  #include "pci.h"
> @@ -90,7 +91,8 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
>  	u32 dword;
>  	int err = 0;
>  
> -	if (!capable(CAP_SYS_ADMIN))
> +	if (!capable(CAP_SYS_ADMIN) ||
> +	    security_locked_down(LOCKDOWN_PCI_ACCESS))
>  		return -EPERM;
>  
>  	dev = pci_get_domain_bus_and_slot(0, bus, dfn);
> diff --git a/include/linux/security.h b/include/linux/security.h
> index a051f21a1144..1b849f10dec6 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -86,6 +86,7 @@ enum lockdown_reason {
>  	LOCKDOWN_DEV_MEM,
>  	LOCKDOWN_KEXEC,
>  	LOCKDOWN_HIBERNATION,
> +	LOCKDOWN_PCI_ACCESS,
>  	LOCKDOWN_INTEGRITY_MAX,
>  	LOCKDOWN_CONFIDENTIALITY_MAX,
>  };
> diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
> index ce5b3da9bd09..e2ee8a16b94c 100644
> --- a/security/lockdown/lockdown.c
> +++ b/security/lockdown/lockdown.c
> @@ -22,6 +22,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
>  	[LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
>  	[LOCKDOWN_KEXEC] = "kexec of unsigned images",
>  	[LOCKDOWN_HIBERNATION] = "hibernation",
> +	[LOCKDOWN_PCI_ACCESS] = "direct PCI access",
>  	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
>  	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
>  };
> -- 
> 2.22.0.410.gd8fdbe21b5-goog
>
diff mbox series

Patch

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 25794c27c7a4..e1011efb5a31 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -903,6 +903,11 @@  static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
 	unsigned int size = count;
 	loff_t init_off = off;
 	u8 *data = (u8 *) buf;
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	if (off > dev->cfg_size)
 		return 0;
@@ -1165,6 +1170,11 @@  static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	int bar = (unsigned long)attr->private;
 	enum pci_mmap_state mmap_type;
 	struct resource *res = &pdev->resource[bar];
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
 		return -EINVAL;
@@ -1241,6 +1251,12 @@  static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
 				     struct bin_attribute *attr, char *buf,
 				     loff_t off, size_t count)
 {
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
+
 	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 6fa1627ce08d..a72258d70407 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -13,6 +13,7 @@ 
 #include <linux/seq_file.h>
 #include <linux/capability.h>
 #include <linux/uaccess.h>
+#include <linux/security.h>
 #include <asm/byteorder.h>
 #include "pci.h"
 
@@ -115,7 +116,11 @@  static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
 	struct pci_dev *dev = PDE_DATA(ino);
 	int pos = *ppos;
 	int size = dev->cfg_size;
-	int cnt;
+	int cnt, ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	if (pos >= size)
 		return 0;
@@ -196,6 +201,10 @@  static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -237,7 +246,8 @@  static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
 	struct pci_filp_private *fpriv = file->private_data;
 	int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
 
-	if (!capable(CAP_SYS_RAWIO))
+	if (!capable(CAP_SYS_RAWIO) ||
+	    security_locked_down(LOCKDOWN_PCI_ACCESS))
 		return -EPERM;
 
 	if (fpriv->mmap_state == pci_mmap_io) {
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index d96626c614f5..31e39558d49d 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -7,6 +7,7 @@ 
 
 #include <linux/errno.h>
 #include <linux/pci.h>
+#include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include "pci.h"
@@ -90,7 +91,8 @@  SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
 	u32 dword;
 	int err = 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) ||
+	    security_locked_down(LOCKDOWN_PCI_ACCESS))
 		return -EPERM;
 
 	dev = pci_get_domain_bus_and_slot(0, bus, dfn);
diff --git a/include/linux/security.h b/include/linux/security.h
index a051f21a1144..1b849f10dec6 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -86,6 +86,7 @@  enum lockdown_reason {
 	LOCKDOWN_DEV_MEM,
 	LOCKDOWN_KEXEC,
 	LOCKDOWN_HIBERNATION,
+	LOCKDOWN_PCI_ACCESS,
 	LOCKDOWN_INTEGRITY_MAX,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index ce5b3da9bd09..e2ee8a16b94c 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -22,6 +22,7 @@  static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
 	[LOCKDOWN_KEXEC] = "kexec of unsigned images",
 	[LOCKDOWN_HIBERNATION] = "hibernation",
+	[LOCKDOWN_PCI_ACCESS] = "direct PCI access",
 	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };